Myeloid inflammatory cells (macrophages, dendritic cells (DC), and infiltrating monocytes) are long lived, TLR4+ cells strategically poised along portals of entry where they perform functions of vital importance to the host. These cells are active participants in innate immunity and orchestrate the transition to and propagation of the adaptive arm of the immune response. Along with these important functions, myeloid inflammatory cells have been implicated in periodontal pathogenesis due to their capacity to secrete copious amounts of proinflammatory cytokines/chemokines and other inflammatory mediators and by serving as osteoclast precursors. Thus modulation of their destructive potential is of great therapeutic interest. While significant progress has been made in elucidating the mechanisms associated with periodontal pathosis, very little is known regarding the role of microRNA (miRNA) in this process. miRNA exerts significant biological effects upon many normal and abnormal cellular functions and it has become increasingly clear that it plays a key role in development and function of the immune response. Moreover, recent reports have begun to highlight their potential value as diagnostic markers. Unfortunately, significant gaps in knowledge are evident regarding the identification and characterization of miRNA in periodontal disease. This is important given the increasing body of evidence implicating dysregulated miRNA profiles in immune-mediated disorders. Our preliminary in-vitro and in-vivo studies have identified candidate miRNAs predicted to target genes linked to myeloid inflammatory cell and osteoclast differentiation and function. These candidate miRNAs were identified from primary myeloid inflammatory cell cultures challenged with periopathic LPS and from gingival tissue specimens derived from periodontally healthy and diseased subjects. As inflammation and bone loss, hallmarks of periodontal disease are mediated in part by the long-lived myeloid inflammatory cell pool, studies focused on the identification and validation of factors selectively modulating their destructive capacity, will advance scientific knowledge and identify new avenues of research and therapy. This proposal seeks to functionally validate candidate miRNAs as modulators of differentiation and function in myeloid inflammatory cells and osteoclasts. Using a systematic approach we will begin by determining the effects of overexpression and knockdown of our candidate miRNAs on myeloid inflammatory cell and osteoclast differentiation. We will also determine the effects on key cellular functions linked to periodontal inflammation and osteoclastogenesis. Thus, this proposal seeks to fill voids in knowledge regarding the role of miRNA in periodontal pathogenesis and provide a basis for the development of animal models that can be genetically manipulated to characterize miRNAs demonstrating significant promise. Ultimately, the goal of which is to identify novel and therapeutically beneficial drug targets that will enhance current treatment modalities. PUBLIC HEALTH RELEVANCE: In the oral cavity, excessive inflammation in response to bacteria can lead to periodontal disease and result in tooth loss. Thus, appropriate control of this inflammatory process is of great therapeutic interest. The focus of our study is to investigate the regulation of endogenous molecules triggering this reaction to prevent excessive inflammation and tooth loss. Knowledge to be gained from this study will be of value to medicine and dentistry.